The present invention relates to phonograph turntables and more particularly to a device for use with phonograph turntables to prevent skating of the turntable tone arm.
In most turntables, as a result of the angle between the line tangent to the record grooves and a line connecting the stylus tip to the tone arm pivot point, a skating force is developed that tends to force the tone arm towards the center of the record. This skating force is proportional to the above described angle, the tracking force applied to the stylus and the coefficient of friction between the stylus and the record groove. Since the angle is constant for a given turntable and the coefficient of friction is approximately constant for a given stylus, the skating force is then equal to some constant multiplied by the tracking force applied to the stylus.
As mentioned above, this skating force tends to drive the arm inwardly towards the center of the record or in other words, it produces a skating torque about the tone arm pivot point. For all standard record players wherein a record rotates in the clockwise direction, the skating force developed is also a clockwise torque around the tone arm horizontal pivot point. The purpose of the anti-skating device is to develop an antiskating force (or torque) to balance out this skating torque.
A number of anti-skating devices have been used in turntables that are now on the market. The most common of these consists of small weights secured to the tone arm that serve to produce torques via attached strings and wires. A problem with these existing devices is that the adjustment of the skating force is limited to discrete steps because of the use of fixed weights and notches for the string at different discrete radii. Other anti-skating devices available use springs and/or magnets to develop an anti-skating torque.
In view of the above, it is the principal object of the present invention to provide an improved anti-skating device adjustable over a continuous range to provide an anti-skating force.